As I restarted the car and drove away from the house, the "driving range" number (which had been at 20 miles) appeared to reset to "---.--"

I drove about 2 miles to a gas station. According to the gas pump, I filled the tank with 17.66 gallons of gas. When I restarted the car, the "driving range" number reset to 300.

Odd, I thought. That seems really low. At an average of 23 miles per gallon and a 18.5 gallon tank, I should see 425 miles in the "driving range". In fact, the last time I filled the tank up, I am pretty sure that the "driving range" number appeared as roughly 400 or 425. (As a side note, my MPG was averaging about 23.4, since I've mostly only done city/suburb driving, since I got the car a couple of weeks ago.)

Over the course of the next few hours, I drove a total of 30 miles (almost exactly). However, the "driving range" number is still reading 300. It didn't move at all.

Wondering if anyone has encountered this problem. I have to take the car to the dealer in the next day or so to get the gas hatch door looked at, and can ask about it at this time. (The gas hatch isn't opening when the lever is pulled and I need a 2nd person to get their fingernails under the hatch when I pull the lever - which is why I had delayed in filling the gas tank up in the first place, but I digress...)

Appreciate thoughts.